The utility of a continuous separation process such as fractional distillation has been recognized for over 30 years. In 1951 C. H. O. Berg described in U.S. Pat. No. 2,539,006 a process whereby gases could be selectively adsorbed onto a solid adsorbent (activated charcoal) in a continuous manner. In this process the adsorbent passed successively through zones of stripping, adsorption, heating, sealing, selective desorption and back to stripping resulting in an effluent gas stream enriched in one or more of the desired components. The apparatus was designed principally for purifying a low molecular weight (less than C.sub.5 's) organic gas stream.
The concept of using a moving bed or a mobile liquid/solid phase counter currently to the flow of the vapor phase in gas liquid chromatography to continuously separate two components was introduced by V. H. Pichler and H. Schulz in an article in Breenstoff-Chemie, Nr. 9/10 Bd. 39, 148 in 1958 and later followed up by P. E. Barker and D. Critsher, Chem. Engng. Sci., 13, 82 (1960) and G. R. Fitch, M. E. Probert and P. F. Tiley, J. Chem. Soc., 4875 (1962). They found in their experiments that a gas stream saturated with at least two components, entering an isothermal column containing a mobile bed moving counter current to the gas stream would under certain conditions elute one of the components with the gas phase while the other component or components, having a greater affinity for the liquid phase, would be retained and ultimately carried to a region where it would be stripped off.
In 1969, P. E. Barker and S. Al-Madfai with the help of Universal Fisher Engineering Company, Crawley, England designed and built a continuous chromatograph employing the principles outlined in the preceding paragraph. The continuous chromatograph was used to purify cyclopentane and cyclohexane; J. Chromatographic Science, 7, 425 (1969).
The major advantage of a continuous chromatography system lies in the prospect that respectable throughputs can be achieved without sacrificing the powerful separating capability of conventional chromatography. L. R. Synder, U.S. Pat. No. 4,204,952May 27, 1980 using tandem chromatographs and seriatim sample injections has attempted to optimize throughput by taking slices from one chromatogram to be used as an input for the second chromatogram; thereby reducing the overall time for any single chromatogram.